The present invention relates to oil ejectors of the type having a nozzle from which a high-velocity stream of motive oil is ejected to entrain pickup oil from a chamber surrounding the nozzle, to form a combined stream which is delivered at a defined pressure to a region to be lubricated.
Many types of large machines, such as turbine generators, include bearings which must be continuously lubricated. The effectiveness of the lubrication depends, inter alia, on the pressure with which the lubricating oil is being supplied to each bearing, there being an optimum oil pressure value for each bearing of a machine. The pressure with which oil is being supplied to each bearing can vary, during operation of the machine, due to a number of factors.
When ejectors of the type described above are used, a primary factor relied upon to set the bearing oil pressure is the cross-sectional area of the output opening or openings provided in the ejector nozzle. The value for this area is selected on the basis of estimated bearing flow and ejector discharge pressure and the known or estimated values for other factors that will influence the bearing oil pressure value.
If, after a machine has been assembled and placed into operation, it should be determined that the initial estimates were inaccurate, or if changes should occur in operating conditions which influence the bearing oil pressure, an adjustment must be made to enable the desired bearing oil pressure value to be achieved. For example, even if the nozzle outlet passage cross-sectional area had been correctly selected to initially provide the required bearing flow, it may be necessary to vary the bearing flow during the operating life of the machine due, for example, to increases in bearing clearances as the result of wear, or changes in system pressure losses due to changes in oil cooler operating mode.
It is current practice to make such an adjustment by physically varying the cross-sectional area of the nozzle outlet passages, either by remachining the nozzle or by replacing it. This, of course, requires shutdown of the entire machine, drainage of the reservoir supplying the pickup oil and disassembly of the ejector. It will be appreciated that machine shutdown, for any purpose, is undesirable and that the disassembly and reassembly required to effect a change in the cross-sectional area of the nozzle outlet openings is both costly and time consuming.